Implement IUnitHandler::notifyUnitSelection

src/common/logging/vst3.cpp

@@ -700,6 +700,16 @@ bool Vst3Logger::log_request(bool is_host_vst,
     });
 }
 
+bool Vst3Logger::log_request(
+    bool is_host_vst,
+    const YaUnitHandler::NotifyUnitSelection& request) {
+    return log_request_base(is_host_vst, [&](auto& message) {
+        message << request.owner_instance_id
+                << ": IUnitHandler::notifyUnitSelection(unitId = "
+                << request.unit_id << ")";
+    });
+}
+
 void Vst3Logger::log_response(bool is_host_vst, const Ack&) {
     log_response_base(is_host_vst, [&](auto& message) { message << "ACK"; });
 }

src/common/logging/vst3.h

@@ -139,6 +139,8 @@ class Vst3Logger {
                      const YaComponentHandler::RestartComponent&);
     bool log_request(bool is_host_vst, const YaHostApplication::GetName&);
     bool log_request(bool is_host_vst, const YaPlugFrame::ResizeView&);
+    bool log_request(bool is_host_vst,
+                     const YaUnitHandler::NotifyUnitSelection&);
 
     void log_response(bool is_host_vst, const Ack&);
     void log_response(

src/common/serialization/vst3.h

@@ -153,7 +153,8 @@ using CallbackRequest = std::variant<WantsConfiguration,
                                      // there
                                      YaConnectionPoint::Notify,
                                      YaHostApplication::GetName,
-                                     YaPlugFrame::ResizeView>;
+                                     YaPlugFrame::ResizeView,
+                                     YaUnitHandler::NotifyUnitSelection>;
 
 template <typename S>
 void serialize(S& s, CallbackRequest& payload) {

src/common/serialization/vst3/component-handler/unit-handler.h

@@ -61,6 +61,25 @@ class YaUnitHandler : public Steinberg::Vst::IUnitHandler {
 
     inline bool supported() const { return arguments.supported; }
 
+    /**
+     * Message to pass through a call to
+     * `IUnitHandler::notifyUnitSelection(unit_id)` to the unit handler provided
+     * by the host.
+     */
+    struct NotifyUnitSelection {
+        using Response = UniversalTResult;
+
+        native_size_t owner_instance_id;
+
+        Steinberg::Vst::UnitID unit_id;
+
+        template <typename S>
+        void serialize(S& s) {
+            s.value8b(owner_instance_id);
+            s.value4b(unit_id);
+        }
+    };
+
     virtual tresult PLUGIN_API
     notifyUnitSelection(Steinberg::Vst::UnitID unitId) override = 0;
     virtual tresult PLUGIN_API